Item QML Type▲
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Import Statement: import QtQuick 2.13
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Inherited By:: AnimatedSprite, AttenuationModelInverse, AttenuationModelLinear, AudioCategory, AudioEngine, AudioListener, AudioSample, BaseKey, Blend, BorderImage, BrightnessContrast, Canvas, Colorize, ColorOverlay, Column, ColumnLayout, ConicalGradient, Control, Desaturate, DirectionalBlur, Displace, DropShadow, FastBlur, Flickable, Flipable, Flow, FocusScope, GammaAdjust, GaussianBlur, Glow, Grid, GridLayout, HandwritingInputPanel, HueSaturation, Image, InnerShadow, InputPanel, KeyIcon, KeyPanel, LevelAdjust, LinearGradient, Loader, LottieAnimation, MaskedBlur, MouseArea, MultiPointTouchArea, OpacityMask, Overlay, ParticlePainter, PathView, PinchArea, PlayVariation, RadialBlur, RadialGradient, Radio, RadioData, Rectangle, RectangularGlow, RecursiveBlur, Repeater, Row, RowLayout, Scene3D, SelectionListItem, ShaderEffect, ShaderEffectSource, Shape, SignalSpy, Sound, SoundInstance, SplitView, SpriteSequence, StackLayout, TestCase, Text, TextEdit, TextInput, ThresholdMask, TraceInputKey, TraceInputKeyPanel, Video, WebEngineView, and ZoomBlur
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Inherits: QtObject
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Group: Item is part of qtquick-visual
Detailed Description▲
The Item type is the base type for all visual items in Qt Quick.
All visual items in Qt Quick inherit from Item. Although an Item object has no visual appearance, it defines all the attributes that are common across visual items, such as x and y position, width and height, anchoring and key handling support.
The Item type can be useful for grouping several items under a single root visual item. For example:
import QtQuick 2.0
Item {
Image {
source: "tile.png"
}
Image {
x: 80
width: 100
height: 100
source: "tile.png"
}
Image {
x: 190
width: 100
height: 100
fillMode: Image.Tile
source: "tile.png"
}
}Key Handling▲
Key handling is available to all Item-based visual types via the Keys attached property. The Keys attached property provides basic signals such as pressed and released, as well as signals for specific keys, such as spacePressed. The example below assigns keyboard focus to the item and handles the left key via the general onPressed handler and the return key via the onReturnPressed handler:
import QtQuick 2.0
Item {
focus: true
Keys.onPressed: {
if (event.key == Qt.Key_Left) {
console.log("move left");
event.accepted = true;
}
}
Keys.onReturnPressed: console.log("Pressed return");
}See the Keys attached property for detailed documentation.
Layout Mirroring▲
Item layouts can be mirrored using the LayoutMirroring attached property. This causes anchors to be horizontally reversed, and also causes items that lay out or position their children (such as ListView or Row) to horizontally reverse the direction of their layouts.
See LayoutMirroring for more details.
Item Layers▲
An Item will normally be rendered directly into the window it belongs to. However, by setting layer.enabled, it is possible to delegate the item and its entire subtree into an offscreen surface. Only the offscreen surface, a texture, will be then drawn into the window.
If it is desired to have a texture size different from that of the item, this is possible using layer.textureSize. To render only a section of the item into the texture, use layer.sourceRect. It is also possible to specify layer.sourceRect so it extends beyond the bounds of the item. In this case, the exterior will be padded with transparent pixels.
The item will use linear interpolation for scaling if layer.smooth is set to true and will use mipmap for downsampling if layer.mipmap is set to true. Mipmapping may improve visual quality of downscaled items. For mipmapping of single Image items, prefer Image::mipmap.
Layer Opacity vs Item Opacity▲
When applying opacity to an item hierarchy the opacity is applied to each item individually. This can lead to undesired visual results when the opacity is applied to a subtree. Consider the following example:
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Non-layered Opacity Sélectionnez |
